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Light-induced changes in stem growth and circumnutations in Helianthus annuus
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Maria Stolarz*, Halina Dziubińska, Elżbieta Król, Maciej Krupa,
Agnieszka Charzewska, Tadeusz Zawadzki, Kazimierz Trębacz |
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Department of Biophysics, Institute of
Biology, Maria Curie-Skłodowska University, Akademicka 19, PL-20-033 Lublin, Poland |
| *email:
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Many studies
including applications of external stimuli like different gravitational forces, touch, high and low
temperature and chemicals have been carried out to understand the mechanisms underling circumnutations.
Circumnutations are defined as helical movements of a growing plant organ. We investigated the effects of
light/dark 16/8h period on stem growth and circumnutations in three-week-old sunflowers. The growth kinetics
was being monitored by an angular position-sensing transducer for a three days and for circumnutation
characteristic the time-lapse images from top view camera were registered and analyzed. Under 24 h light/dark
cycle both the stem growth and circumnutation parameters displayed diurnal rhythm . Besides long-lasting
fluctuation in a range of many hours, the light- induced short sunflower stem response in a range of a few
minutes were observed. After switching on the light a rapid decrease of the growth rate and even a stem
contraction was observed. The kinetics of stem reaction had a characteristic wave-like shape and all in all
persisted about 60 minutes. These drastic changes in stem length were accompanied by phase dependent
circumnutation disturbances. These results suggest that after non-injured light stimuli hydro-electrochemical
signals which might interfere with circumnutation mechanism appeared in sunflower stem. |
